Influence of casting solvent on phenyl ordering at the surface of spin cast polymer thin films

• Published in: Journal of colloid and interface science Vol. 423; no. 423; pp. 60 - 66
• Main Authors: Myers, John N., Zhang, Chi, Chen, Chunyan, Chen, Zhan
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 01.06.2014; Elsevier
• Subjects: Air - analysis; Applied sciences; Aromaticity; Benzene Derivatives - chemistry; Benzhydryl Compounds - chemistry; Centrifugal casting; Exact sciences and technology; Machinery and processing; Miscellaneous; Molecular structure; Order disorder; Phenyls; Plastics; Polymer industry, paints, wood; Polymer thin film; Polymeric films; Polymers - chemistry; Polymethacrylic Acids - chemistry; Siloxanes - chemistry; Solvents; Solvents - chemistry; Spectrophotometry, Infrared; Spectroscopy; Spin coating; Sulfones - chemistry; Sum frequency generation spectroscopy; Surface Properties; Surface structure; Technology of polymers; Thin films; Vibrational spectroscopy; Sum frequency generation spectroscopy; Polymer thin film; Molecular structure; Spin coating; Surface structure; Vibrational spectroscopy; Solvent effect; Gas liquid interface; Methacrylate polymer; Sulfone polymer; Experimental study; Thin film; Aryl methacrylate polymer; Spin-on coating; Polycarbonate; Siloxane polymer
• DOI: 10.1016/j.jcis.2014.02.027
• ISSN: 0021-9797

[Display omitted] •Molecular structures of spin coated polymer thin films elucidated using surface sensitive spectroscopy.•Different solvents used in spin-coating resulted in varied molecular surface structures.•Aromaticity of the solvent mediated surface phenyl group orientation on the surface. Controlling the surface molecular structure of spin cast polymer films is important for the rational design of surface properties. However, the relationship between spin casting parameters and film surface molecular structure is poorly understood. We report that the surface molecular structure of spin cast homopolymers which contain phenyl groups is influenced by the solvent aromaticity, investigated by a nonlinear optical spectroscopy, sum frequency generation (SFG) vibrational spectroscopy. When phenyl groups were located in a linear polymer backbone, spin casting with aromatic solvents enhanced the phenyl SFG signal relative to when a non-aromatic solvent was used which suggests that the aromatic solvent induced the surface phenyl groups to be more ordered and/or to lie more perpendicular to the film surface. In addition, when alkyl structures were believed to be present at the solvent/air interface, alkyl structures were observed at the film/air interface which suggests that molecular structure at the solvent/air interface was carried to the film surface. The effects of solvent aromaticity on phenyl ordering at spin cast film surfaces can be explained by different molecular structures of polymer chains at solvent/air interfaces, preferential solvation of functional groups during evaporation, and re-orientation of bulky side groups at the polymer film/air interface.